A photoreactive system may include a solid-state lighting array to curing photo sensitive media such as coatings, including inks, adhesives, preservatives, etc. Curing time of these photo sensitive media may be responsive to solid-state lighting array irradiance output. Further, solid-state lighting array irradiance output may be influenced by temperatures of solid-state lighting devices that make up the solid-state lighting array. Therefore, if the solid-state lighting devices operate at temperatures away from their nominal operating temperature, photo sensitive media may not cure sufficiently or electrical power consumption may increase due to changes in solid-state light device irradiance levels. Additionally, the solid-state lighting devices may be in thermal communication with a heat sink to control solid-state lighting device temperature. However, the heat sink may have several temperature zones that vary in temperature from other temperature zones of the heat sink. Consequently, some solid-state lighting devices in the solid-state lighting array may operate at different temperatures than other solid-state lighting devices in the solid-state lighting array. As a result, irradiance output from one area of the lighting array may vary more than is desired from irradiance output from a different area of the lighting array, especially if the lighting arrays are operated independently.
The inventor herein has recognized the above-mentioned disadvantages and has developed a system for operating one or more light emitting devices, comprising: at least two independently controlled lighting arrays comprised of at least one light emitting device; and an amplifier including a negative feedback loop, at least two negative temperature coefficient devices electrically coupled in parallel and included in the negative feedback loop, each of the at least two negative temperature coefficient devices in thermal communication with one of the at least two independently controlled lighting arrays.
By electrically coupling two or more negative temperature coefficient devices in parallel and in a negative feedback loop of an amplifier that controls current flow through one or more light emitting devices, it may be possible to control irradiance output of two or more lighting arrays in a photoreactive system with a single amplifier. The inventor has recognized that one negative temperature coefficient device in a parallel electrical circuit with other negative temperature coefficient devices may dominate determination of amplifier gain such that amplifier gain is more influenced by the one negative temperature coefficient device than other negative temperature coefficient devices in the parallel electrical circuit when a lighting array monitored by the one negative temperature coefficient device is active while other lighting arrays monitored by other negative temperature coefficient devices are inactive. Consequently, the amplifier gain may be appropriate for the activated lighting array monitored by the one negative temperature coefficient device. In one example, two or more negative temperature coefficient devices are in thermal communication with two or more lighting arrays via a heat sink. The temperatures sampled at the heat sink via the two or more negative temperature coefficient devices supply temperature feedback for the individual lighting arrays to the amplifier so that irradiance of each lighting array may be controlled to provide a desired level of irradiance for the photoreactive system.
The present description may provide several advantages. Specifically, the approach may improve lighting system light intensity control. Additionally, the approach may provide feedback control for more than two independently controlled lighting arrays via a single amplifier. Further, the approach may provide more consistent curing of photo sensitive media.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.